1. Field of the Invention
The present invention relates to wrench having a ratchet wheel and more particularly to an improved mechanism for changing direction of exerted force of wrench having a ratchet wheel.
2. Description of Related Art
Mechanisms for changing direction of exerted force of wrench having a ratchet wheel are well known. For example, Taiwanese Patent Published No. 90,220,645 disclosed an enclosed box portion 1 of a wrench as shown in FIG. 1 in which in the enclosed box portion 1 there are provided a circular opening 2, a crescent cavity 3 adjacent its handle and being in communication with the opening 2, two spaced recesses 4 in a wall of the cavity 3, a ratchet wheel 5 having a central opening, the ratchet wheel 5 being fitted in the opening 2, two pawls 6 in the cavity 3, each pawl 6 having one end formed as a rotary member 8 in the recess 4, a spring 10 anchored between the wall of the cavity 3 and one side of the pawl 6 so as to bias a toothed section 8 of the pawl 6 to engage with teeth of the ratchet wheel 5, and a swing member 9 interengaged the pawls 6, the swing member 9 being adapted to move toward either side to disengage one pawl 6 from the ratchet wheel 5 responsive to a clockwise rotation or counterclockwise rotation of the wrench. Such mechanism for changing direction of exerted force of the wrench has the drawbacks of easily damaging the pawls 6, being difficult of manufacturing, and having reduced number of teeth interengaged the pawls 6 and the ratchet wheel 5.
Another Taiwanese Patent Published No. 91,201,915 disclosed an enclosed box portion 11 of a wrench as shown in FIG. 2 in which in the enclosed box portion 11 there are provided a circular opening 12, a crescent cavity 13 adjacent its handle and being in communication with the opening 12, a recess 14 in a center of a wall of the cavity 13, an inner spring 15 in the recess 14, an outer steel ball 16 in a mouth of the recess 14, a pawl 17 in the cavity 13, one side of the pawl 17 being biased by the spring depressible steel ball 16, a C-ring 18 in the opening 12, the C-ring 18 having its opening being tightly engaged with a projecting toothed section of the pawl 17, and a ratchet wheel 19 enclosed by the C-ring 18. In operation, the pawl 17 moves toward either side to engage itself with the ratchet wheel 19 or not responsive to a clockwise rotation or counterclockwise rotation of the wrench. Such mechanism for changing direction of exerted force of the wrench still has the drawbacks of having a relatively large number of components required to cooperate each other very well which in most cases cannot be obtained, and being difficult of manufacturing.
Still another Taiwanese Patent Published No. 87,205,173,A02 disclosed an enclosed box portion 1 of a wrench as shown in FIG. 3 in which in the enclosed box portion 20 there are provided a ratchet wheel 21 in a circular opening, a pawl 22 in a crescent cavity adjacent its handle and the crescent cavity being in communication with the circular opening, and a swing member 23 in a recess in a wall of the crescent cavity, the swing member 23 having a projecting, spring depressible pin 24 urged against the pawl 22 to cause the pawl 22 to engage with the ratchet wheel 21. In operation, the pawl 22 moves toward either side to engage itself with the ratchet wheel 21 or not responsive to a clockwise rotation or counterclockwise rotation of the wrench. Such mechanism for changing direction of exerted force of the wrench still has the drawbacks of having a relatively large number of components required to cooperate each other very well which in most cases cannot be obtained, being inconvenient in operation, and poor direction change of exerted force. Thus, the need for improvement still exists.